The spoon is 3.5 inches long with a bowl diameter of .75 inches. There are no identifying marks on the spoon. The front and back of the bowl are embossed with figures and characters which are worn near the edge of the bowl.
The winged lion with aureole and Gospel book is the crest of the ancient Republic of Venice so PBK is right on the money. Here is a spoon with the finial like yours
The image on the bowl looks a lot like that on many ancient Byzantine coins (ca. 900 A.D.). I've personally cleaned many of these shortly after they were found.